DSN stands for the Defense Switched Network which is a global phone service used by the United States government capable of both non-secure and secure communications. Traditionally, the DSN network has only been used for voice communications, but in the past decade data and video service have been incorporated into the network through Integrated Services Digital Network (ISDN) connections. Secure DSN phone calls are made through the combined use of a Secture Terminal Equipment (STE) or Secure Telephone Units (STUs). Although the U.S. Department of Defense (DoD) is the largest user of the network, other federal agencies, allied countries, and contractors are also authorized users of the DSN network.

What Organizations Use the DSN Network?

The majority of Department of Defense (DoD) commands have one or more phone lines in the DSN network. Just because a command has a DSN phone number, however, does not mean that the number(s) will automatically be listed in the global DSN directory. The command has to formally request via the Defense Information Systems Agency (DISA) to be listed in the directory.How to Dial a DSN Number

Steps to Dial a DSN Number

Although the DSN phone network can be accessed by a commercial phone at a command or agency that is an authorized network user, they can not be called from a personal or home phone.

Step 1 – Confirm the access numbers to dial on your phone to access the DSN network. Typically this will be a one or two digit combination such as “88,” “89”, or “99.”

Step 2 – Dial the DSN area code for the geographic region that you are calling. If you are dialing a DSN phone number for the same region that you are located, this step can be omitted. The DSN area codes are:

Continental US/Puerto Rico – 312, 502 for video calls
Europe – 314, 504 for video calls
Pacific – 315, 505 for video calls
Alaska – 317, 507 for video calls
Central Command (Southwest Asia)- 318, 504 for video calls
Canada – 319, 509 for video calls

Step 3 – Dial the seven digit DSN phone number and complete the phone call as you would with a commercial phone line.

Step 4 – If you need to make a secure phone call, you will need to follow the procedures at your command or organization to initiate a secure call after the person you are calling answers the phone.